Slightly more than half of Contra Costa County’s 520,000 registered voters live in cities or other political districts with an election set for Nov. 3.

These voters include those who’ll decide on a vacant congressional seat, and those who’ll cast ballots in San Ramon, Walnut Creek and two school districts.

Voters in Newark, Emeryville and Albany also will participate in the typically small off-year election cycle.

Residents in these communities began receiving this week their vote-by-mail ballots, a voting method again expected to substantially eclipse the numbers of those who cast their votes at the polls.

The highest profile race is the runoff to replace former Rep. Ellen Tauscher in the 10th Congressional District. Two-thirds of the heavily Democratic district is in Contra Costa, with smaller segments in Alameda, Solano and Sacramento counties.

The U.S. Senate confirmed Tauscher in June as undersecretary for arms control and international security in the U.S. State Department.

Democrat and Lt. Gov. John Garamendi is the front-runner by virtue of his political party and high name identification. He faces GOP nominee and Dougherty Valley attorney David Harmer. The names of three minor-party candidates also will appear on the ballot.

The congressional contest coupled with Walnut Creek’s two school funding measures and its seemingly perennial battle over downtown development could easily drive up voter turnout there.

Walnut Creek voters will decide the fate of Measure I, a contentious initiative that would grant Broadway Plaza owner Macerich Co. permission to build a new store downtown intended for a Neiman Marcus.

Residents of the Acalanes and Walnut Creek school districts also will decide whether to extend indefinitely existing parcel taxes that help close the state funding gap. The measures require a difficult two-thirds vote threshold but there has been little organized opposition.

Violent police encounters in California last year led to the deaths of 157 people and six officers, the state attorney general’s office said Thursday in a report that provides the first statewide tally on police use-of-force incidents.

At 6:03 p.m. Wednesday, police responded to reports of the robbery at the facility, 2301 Bancroft way, and learned that a man who snuck into the facility and began prowling through the building, taking cell phones and wallets from victims.

Investigators’ efforts to solve the case led to the arrests of Pablo Mendoza, 25, of Hayward, Brandon Follings, 26, of Oakland and Valeria Boden, 26, of Alameda, the Alameda County Sheriff’s Office said Thursday.